<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>参考链接：https://codepen.io/Chokcoco/pen/KKmvYor</title>
	</head>
	<style type="text/css">
		body {
			background-color: #000;
			margin: 0;
			overflow: hidden;
			background-repeat: no-repeat;
		}
	</style>
	<body>
		<canvas id="canvas" width="1400" height="600"></canvas>
	</body>
	<script type="text/javascript">
		var canvas = document.getElementById("canvas");

		canvas.width = window.innerWidth;
		canvas.height = window.innerHeight;

		// Initialize the GL context
		var gl = canvas.getContext("webgl");
		if (!gl) {
			console.error("Unable to initialize WebGL.");
		}

		//Time
		var time = 0.0;

		//************** Shader sources **************

		var vertexSource = `
		attribute vec2 position;
		void main() {
			gl_Position = vec4(position, 0.0, 1.0);
		}
		`;

		var fragmentSource = `
		precision highp float;
		
		uniform float width;
		uniform float height;
		vec2 resolution = vec2(width, height);
		
		uniform float time;
		
		#define POINT_COUNT 8
		
		vec2 points[POINT_COUNT];
		const float speed = -0.5;
		const float len = 0.25;
		float intensity = 1.3;
		float radius = 0.008;
		
		//https://www.shadertoy.com/view/MlKcDD
		//Signed distance to a quadratic bezier
		float sdBezier(vec2 pos, vec2 A, vec2 B, vec2 C){    
			vec2 a = B - A;
			vec2 b = A - 2.0*B + C;
			vec2 c = a * 2.0;
			vec2 d = A - pos;
		
			float kk = 1.0 / dot(b,b);
			float kx = kk * dot(a,b);
			float ky = kk * (2.0*dot(a,a)+dot(d,b)) / 3.0;
			float kz = kk * dot(d,a);      
		
			float res = 0.0;
		
			float p = ky - kx*kx;
			float p3 = p*p*p;
			float q = kx*(2.0*kx*kx - 3.0*ky) + kz;
			float h = q*q + 4.0*p3;
		
			if(h >= 0.0){ 
				h = sqrt(h);
				vec2 x = (vec2(h, -h) - q) / 2.0;
				vec2 uv = sign(x)*pow(abs(x), vec2(1.0/3.0));
				float t = uv.x + uv.y - kx;
				t = clamp( t, 0.0, 1.0 );
		
				// 1 root
				vec2 qos = d + (c + b*t)*t;
				res = length(qos);
			}else{
				float z = sqrt(-p);
				float v = acos( q/(p*z*2.0) ) / 3.0;
				float m = cos(v);
				float n = sin(v)*1.732050808;
				vec3 t = vec3(m + m, -n - m, n - m) * z - kx;
				t = clamp( t, 0.0, 1.0 );
		
				// 3 roots
				vec2 qos = d + (c + b*t.x)*t.x;
				float dis = dot(qos,qos);
		        
				res = dis;
		
				qos = d + (c + b*t.y)*t.y;
				dis = dot(qos,qos);
				res = min(res,dis);
				
				qos = d + (c + b*t.z)*t.z;
				dis = dot(qos,qos);
				res = min(res,dis);
		
				res = sqrt( res );
			}
		    
			return res;
		}
		
		
		//http://mathworld.wolfram.com/HeartCurve.html
		vec2 getHeartPosition(float t){
			return vec2(16.0 * sin(t) * sin(t) * sin(t),
									-(13.0 * cos(t) - 5.0 * cos(2.0*t)
									- 2.0 * cos(3.0*t) - cos(4.0*t)));
		}
		
		//https://www.shadertoy.com/view/3s3GDn
		float getGlow(float dist, float radius, float intensity){
			return pow(radius/dist, intensity);
		}
		
		float getSegment(float t, vec2 pos, float offset, float scale){
			for(int i = 0; i < POINT_COUNT; i++){
				points[i] = getHeartPosition(offset + float(i)*len + fract(speed * t) * 6.28);
			}
		    
			vec2 c = (points[0] + points[1]) / 2.0;
			vec2 c_prev;
			float dist = 10000.0;
		    
			for(int i = 0; i < POINT_COUNT-1; i++){
				//https://tinyurl.com/y2htbwkm
				c_prev = c;
				c = (points[i] + points[i+1]) / 2.0;
				dist = min(dist, sdBezier(pos, scale * c_prev, scale * points[i], scale * c));
			}
			return max(0.0, dist);
		}
		
		void main(){
			vec2 uv = gl_FragCoord.xy/resolution.xy;
			float widthHeightRatio = resolution.x/resolution.y;
			vec2 centre = vec2(0.5, 0.5);
			vec2 pos = centre - uv;
			pos.y /= widthHeightRatio;
			//Shift upwards to centre heart
			pos.y += 0.02;
			float scale = 0.000015 * height;
			
			float t = time;
		    
			//Get first segment
		  float dist = getSegment(t, pos, 0.0, scale);
		  float glow = getGlow(dist, radius, intensity);
		  
		  vec3 col = vec3(0.0);
		
			//White core
		  col += 10.0*vec3(smoothstep(0.003, 0.001, dist));
		  //Pink glow
		  col += glow * vec3(1.0,0.05,0.3);
		  
		  //Get second segment
		  dist = getSegment(t, pos, 3.4, scale);
		  glow = getGlow(dist, radius, intensity);
		  
		  //White core
		  col += 10.0*vec3(smoothstep(0.003, 0.001, dist));
		  //Blue glow
		  col += glow * vec3(0.1,0.4,1.0);
		        
			//Tone mapping
			col = 1.0 - exp(-col);
		
			//Gamma
			col = pow(col, vec3(0.4545));
		
			//Output to screen
		 	gl_FragColor = vec4(col,1.0);
		}
		`;

		//************** Utility functions **************

		window.addEventListener("resize", onWindowResize, false);

		function onWindowResize() {
			canvas.width = window.innerWidth;
			canvas.height = window.innerHeight;
			gl.viewport(0, 0, canvas.width, canvas.height);
			gl.uniform1f(widthHandle, window.innerWidth);
			gl.uniform1f(heightHandle, window.innerHeight);
		}

		//Compile shader and combine with source
		function compileShader(shaderSource, shaderType) {
			var shader = gl.createShader(shaderType);
			gl.shaderSource(shader, shaderSource);
			gl.compileShader(shader);
			if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
				throw "Shader compile failed with: " + gl.getShaderInfoLog(shader);
			}
			return shader;
		}

		//From https://codepen.io/jlfwong/pen/GqmroZ
		//Utility to complain loudly if we fail to find the attribute/uniform
		function getAttribLocation(program, name) {
			var attributeLocation = gl.getAttribLocation(program, name);
			if (attributeLocation === -1) {
				throw "Cannot find attribute " + name + ".";
			}
			return attributeLocation;
		}

		function getUniformLocation(program, name) {
			var attributeLocation = gl.getUniformLocation(program, name);
			if (attributeLocation === -1) {
				throw "Cannot find uniform " + name + ".";
			}
			return attributeLocation;
		}

		//************** Create shaders **************

		//Create vertex and fragment shaders
		var vertexShader = compileShader(vertexSource, gl.VERTEX_SHADER);
		var fragmentShader = compileShader(fragmentSource, gl.FRAGMENT_SHADER);

		//Create shader programs
		var program = gl.createProgram();
		gl.attachShader(program, vertexShader);
		gl.attachShader(program, fragmentShader);
		gl.linkProgram(program);

		gl.useProgram(program);

		//Set up rectangle covering entire canvas
		var vertexData = new Float32Array([
			-1.0,
			1.0, // top left
			-1.0,
			-1.0, // bottom left
			1.0,
			1.0, // top right
			1.0,
			-1.0 // bottom right
		]);

		//Create vertex buffer
		var vertexDataBuffer = gl.createBuffer();
		gl.bindBuffer(gl.ARRAY_BUFFER, vertexDataBuffer);
		gl.bufferData(gl.ARRAY_BUFFER, vertexData, gl.STATIC_DRAW);

		// Layout of our data in the vertex buffer
		var positionHandle = getAttribLocation(program, "position");

		gl.enableVertexAttribArray(positionHandle);
		gl.vertexAttribPointer(
			positionHandle,
			2, // position is a vec2 (2 values per component)
			gl.FLOAT, // each component is a float
			false, // don't normalize values
			2 * 4, // two 4 byte float components per vertex (32 bit float is 4 bytes)
			0 // how many bytes inside the buffer to start from
		);

		//Set uniform handle
		var timeHandle = getUniformLocation(program, "time");
		var widthHandle = getUniformLocation(program, "width");
		var heightHandle = getUniformLocation(program, "height");

		gl.uniform1f(widthHandle, window.innerWidth);
		gl.uniform1f(heightHandle, window.innerHeight);

		var lastFrame = Date.now();
		var thisFrame;

		function draw() {
			//Update time
			thisFrame = Date.now();
			time += (thisFrame - lastFrame) / 1000;
			lastFrame = thisFrame;

			//Send uniforms to program
			gl.uniform1f(timeHandle, time);
			//Draw a triangle strip connecting vertices 0-4
			gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

			requestAnimationFrame(draw);
		}

		draw();
	</script>
</html>
